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smurfkiller

lua error handling

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Is there a way to hook a custom error function when a lua error occurres? For example if i want display a message box with error information in a windows application instead of stdout in a console app. There is a library function called lua_atpanic that can be used in unprotected mode. How do i know if im running in protected or unprotected mode? Why is there so extreamly low on information about this? It should be as simple as setting a custom error callback. Unless you coding a console application you will not see any lua errors. Only way is to redirect stdout in some way.

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lua_atpanic

Quote:

lua_CFunction lua_atpanic (lua_State *L, lua_CFunction panicf);

Sets a new panic function and returns the old one.

If an error happens outside any protected environment, Lua calls a panic function and then calls exit(EXIT_FAILURE), thus exiting the host application. Your panic function can avoid this exit by never returning (e.g., doing a long jump).

The panic function can access the error message at the top of the stack.

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Sorry, didn't see you had already found atpanic. Functions called with lua_cpcall or lua_pcall are protected, all others are not (I think.)

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Quote:
How do i know if im running in protected or unprotected mode
If you are using lua_call and not lua_pcall or lua_cpcall then you are in unprotected mode.

Quote:
Why is there so extreamly low on information about this?

There is? There is a section in Programming in Lua second edition on this matter.

Quote:
Is there a way to hook a custom error function when a lua error occurres? For example if i want display a message box with error information in a windows application instead of stdout in a console app.

Yes using one of the calls listed above or checking the return codes of the functions. If using C or have Lua compiled in C and you set a lua_atpanic function and return from this function the program will exit, if this is not what you want then you must set up your own long jump and then long jump to it from the function. If you compile Lua using C++ then Lua will throw exceptions IIRC.
edit : ninja'd whilst looking for links

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Will try that thanks! Tho, 'lua_atpanic' seems like a strange function name for it's purpose. If it where called 'lua_onerror' i wouldn't have to even ask in forum about it.

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Not sure about other LUA calling functions, but if you call lua_pcall on a chunk and it fails in some way, the LUA error string is pushed onto the stack and can be accessed with lua_tostring(L, -1); You can put this in a message box if you want.

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